Fix: Issue 10520 - [profile+nothrow] Building with profiler results in "is not nothrow" error on some contracts

When Statement#blockExit() checks if the statements may throw or not, it
can also emit compile error.
We turn the second argument of it, mustNotThrow, to false
so that the error is suppressed.
Fix issue 12965 - DMD sets ELFOSABI to ELFOSABI_LINUX on all systems
Fixed comment alignment; added #error for undefined ELF ABIs
fix Issue 12970 - Enclosing @system attribute is precedence than postfix @safe
Merge pull request #3687 from jasonbking/osabi

Fix issue 12965 - DMD sets ELFOSABI to ELFOSABI_LINUX on all systems
Fix Linux/64 compile error.
Merge pull request #3691 from quickfur/missing_endif

Fix Linux/64 compile error introduced by pull #1296
Fix issue 12968 - Incorrect codgen for xchg with R8
Merge pull request #3690 from Orvid/issue12968

Fix issue 12968 - incorrect codegen
Ddoc should output qualified anchors for template members.

Fixes [issue 10366] (https://issues.dlang.org/show_bug.cgi?id=10366).
Add tests for issue 10366.
Update ddoc test outputs to have qualified anchors.
Merge pull request #3693 from quickfur/ddoc_qualified_anchors

Implement ddoc qualified anchors for template members
Merge pull request #3688 from 9rnsr/fix12970

Issue 12970 - Enclosing @system attribute is precedence than postfix @safe
fix Issue 12900 - Wrong code in IfStatement condition Expression
[WS] Replace tab with spaces.

Tab was added in d8e5f55c9b94e831b6d178a20e34144933c3fc32.
Merge pull request #3694 from denis-sh/ws-fixup-pull-3687

[Whitespace] Replace tab with spaces.
fix Issue 12967 - Prefix method 'this' qualifiers should be disallowed in DeclDefs scope
Check redundant/conflicting attributes between prefix and postfix
Fix another broken case of qualified anchors.

The previous fix didn't work for template members of templated structs.